I am not sure what exactly is incorrect about the last video you showed.
Paper2D uses a specialized physics system (Box2D) that tries to force character orientations.
the biggest issue I see in your initial video here is that the camera is skewed, which I feel is a result of taking the rotator, and multiplying it by a scalar of 2?? (if you take a rotator of <Y:10, P:15, R:0> you will get <Y:20, P:30, R:0> which is very different orientation)
as for in 3D setting the Character’s Gravity Orientation (as of UE5.4) mostly trial
you can see some of the problems that the camera gets into, and to fix that stuff you need to do work on either the CameraController, CharacterController, or the CharacterMovementComponent which any of those would need at least a little C++ (each of these are available with some searching online for something like “Unreal Engine Gravity Camera”), but will in most cases require changing the the input processing for look and movement.